Electron discharge device



Nov. 24, 1942. J. P. LAICO ELECT-RON DISCHARGE DEVICE Filed Jan. 21, 1941 FIG. 2

AT TORNEV Patented Nov. 24, 1942 HIECTBON DISCHARGE DEVICE Joseph I. Laico, Brooklyn, N. IL, assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,' a corporation of New York Application January 21, 1941, Serial No. 375,111

3Clalms.

This invention relates to electron discharge devices and more particularly to electrode systems, .commonly referred to as electron guns, for

' such devices of the beam type.

/ efilcient concentration of these electrons and sensiti've and accurate control of the beam entails the use of electrodes of special forms and the mounting thereof in fairly critical physical relation with the cathode and with one another. Hence, the construction of an efiicient, high quality electron gun has involved exacting and detailed work. with consequent expense. When such a gun becomes inoperative, due in most cases to failure of the cathode, considerable expense is incurred in replacing the gun in the device in which it is incorporated or in rebuilding the gun with the view of again utilizing component parts thereof.

Objects of this invention, therefore, are to simplify the construction of multielectrode electron guns and to expedite the construction and repair thereof.

In one illustrative embodiment of this invention, an electron discharge device comprises a cathode including a metallic member a portion of which is coated with electron emissive material, a heater element for the cathode, and a pair of electrodes in cooperative relation with the cathode for concentrating the electrons emanating therefrom into an electron beam.

In accordance with one feature of this invention, the electron gun is fabricated as a unitary assembly from which the cathode and the heater element are readily removable as a unit and this unit and one of the electrodes are provided with cooperating means whereby the unit are similar one may be inserted into the assembly and automatically positioned so that the requisite exact relation'of the cathode with respect to the other 'elecrodes of the assembly is realized.

Fig. 1 is an elevational view mainly in section" of an electron beam discharge device including this invention;

Fig. 2 is an enlarged sectional view of the electron gun, included in the discharge device shown in Fig. 1; and 4 Fig. 3 is an end view of the electron gun taken along plane 3-3 of Fig. 2.

Referring now to the drawing, the electron discharge device shown in Fig. 1 is of the velocity variation beam type and comprises an elongated, evacuated enclosing vessel III of vitreous material and having inwardly extending, axially aligned stems II and I2 at opposite ends thereof. An electron gun, designated generally as I3 and described in detail hereinafter, is mounted on the stem II and a recessed anode or target electrode I4 is mounted on the other stem I2 in axial alignment with the electron gun I3.

Monuted between the electron gun I3 and anode or target electrode I4 are a plurality of centrally apertured electrodes I5 to I9, inclusive, in axial alignment with the electron gun I3 and in energy translating relationship with the electron beam flowing between the electron gun and the anode or target electrode. As shown clearly in Fig. 1, the electrodes I5 and I8 define a gap II and the electrodes I8 and I9 define a second gap 2|, at which gaps energy may be imparted to 4 or taken from the electron beam through the agency of external circuits, not shown, suitably associated with the various electrodes. Each of the electrodes I5 to I9, inclusive, includes an annular disc portion extending through the side of the enclosing vessel I0 and hermetically sealed thereto. The electrodes may be provided with annular corrugations, as illustrated in the electrodes I6, I! and I8, to allow accurate relative positioning thereof during assembly of the device and to prevent deleterious disturbance of this relation by expansion and contractionof the electrodes due to variations in the temperature thereof during construction and operation of the device.

The electron gun I3, as shown clearly in Fig. 2, is constructed as a unitary assembly the foundation of which is an insulating ring 22, for example, of glass. This assembly comprises a pair of rigid, cylindrical beam forming electrodes 23 and 24, for example of a magnetic material such as steel. mounted one within the other and supported in exact coaxial relation by a plurality of rigid supports 25 and 26, respectively, embedded in the insulating ring 22, the electrodes 23 and 24 having surfaces 21 and 28, respectively, of predetermined configuration and in 2 predetermined space relation such as described for example, in the application, Serial No. 328,826, filed April 4, 1940, of Arthur L. Samuel and Carlyle V. Parker.

The unitary assembly includes also a cathode including a cylindrical cup-shaped metallic member 29, the base 30 of which is arched inwardly and conforms to a segment of a sphere andthe surface 3| of the base being coated with a material having good thermionic emission characteristics. Mounted within the cathode and in proximity to the base 30 thereof is a heater element which includes a pair of relatively wide diameter heater coils .32 embedded in an insulating, preferably ceramic, mass 33.

The end portions 34 of the heater coil are sealed in an insulating bead 35 in an aperture in a metallic cup-shaped member 38 fitted within the cathode and locked in position by tabs 31 struck from the body of the cathode. Heating current to the coil 32 is supplied through leading-in conductors 38 sealed in the stem H and spaced from one another by insulating sleeves 39. As shown in Fig. 2, the heater coil comprises two similar parts oppositely wound, in order that, when energized, it will not produce a magnetic field deleteriously affecting the fields adjacent the cathode surface 3|.

As shown in Fig. 2, the cup-shaped member 33 is constructed of two or more layers in order to conserve the heat produced by the heater coil. Conservation of this heat is provided also by a pair of metallic baffles 40 and 4| joined to one another in spaced relation and one of which is secured to the cathode as shown.

The cathode and heater unit is slidably insertable into the inner electrode 23 through an annular flange or guide 42 on the electrode 23, which locates the unit in exact coaxial relation with the electrode 23, the cathode being provided with an annular stop 43 which abuts the lower end of the electrode 23 and locates the cathode heater unit whereby the requisite exact spacing of the emissive surface 3| with respect to the surfaces 21 and 28 is established automatically when the cathode-heater unit is inserted into place. This unit is held in position by a plurality of rigid relatively thin wires 44 secured to the baffle 4| and to rigid metallic uprights l5 aflixed to the electrode 23 and sealed in the stem The uprights 45 are embedded in the stem H and constitute the supports for the electron If the electron gun should become inoperative, as by failure of the emissive surface 3| or of the heater element, the electron gun together with the stem II on which it is mountedmay be removed as a unit from the enclosing vesseiby cutting the wall of the enclosing vessel at a region in the vicinity of the stem II. The wires 38 and 44 may then be severed and the cathodeheater assembly withdrawn as a unit. A similar cathode-heater assembly is then inserted into the electrode 23 and, as has been noted hereinabove, this assembly will be positioned accurately so that the requisite exact spacing of the emissive surface 3| of the cathode with respect to the surfaces 21 and 23 is realized readily. It will be noted that this replacement of the cathode and heater is accomplished without affecting the relation of the beam forming electrodes 23 and 24.

Although a specific embodiment of the invention has been shown and described, it will be understood, of course, that it is only illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. An electron gun for electron discharge devices comprising a foundation member, a pair of cooperating electrodes mounted on said foundation member and fixed in spaced relation thereby, one of said electrodes including a cylindrical portion, a unitary assembly extending within and slidably fitted in said cylindrical portion and including a cathode and a heater element therefor, and cooperating means on said one electrode and said assembly for positioning said assembly longitudinally with respect to said one electrode.

2. A unitary electron gun assembly for electron discharge devices comprising an annular insulating member, a pair of coaxial electrodes the inner of which has a cylindrical portion provided with an inwardly extending flange, means extending from said insulating member and supporting said electrodes in fixed relation, a unitary assembly insertable within said inner electrode and coaxial therewith, said assembly including a cathode member having a cylindrical portion slidably fitted within said flange and provided with a stop for abutting said flange to locate said assembly longitudinally with respect to said inner electrode, and wire means secured to one of said electrodes for locking said assembly in position.

3. A unitary assembly for electron discharge devices comprising a stem, a pair of coaxial electrodes the inner of which has a cylindrical portion provided with an inwardly extending annular flange, rigid means supporting said inner electrode from said stem, an insulating member fixedly supporting from said inner electrode, rigid means mounting the other of said electrodes from said insulating member, a cathode member having a cylindrical portion slidable in said annular flange and provided with an annular stop adapted to abut said flange when said cathode is inserted through said flange, a heater element mounted within said cathode member, and a plurality of rigid wires secured to said first rigid means and to said cathode member and locking .said cathode member in position within said inner electrode.

JOSEPH P. LAICO. 

